It is known practice with control devices for roller blinds to determine an intermediate position of the roller blind, termed the shading and ventilation position, which can be stored in memory by the installer or by the user.
In the case of a roller blind with perforated slats, the shading and ventilation position is such that the shutter curtain of the blind is almost fully unwound, the slats remaining separated from each other. In this separated position of the slats, elongate holes can be seen in the top of each slat. These are normally hidden when the slats are resting on top of each other, as shown in FIG. 1. Such a situation provides the room with privacy from the exterior and provides attenuated lighting, while allowing ventilation if the windows are not shut.
This position typically corresponds to 80–90% of the movement of the winding drum of the blind required to close the blind. However, this position depends very much on the type of roller blind slats used in the construction of the shutter curtain.
EP 0 426 577 discloses just such a means of storing in memory an intermediate position and executing an instruction designed to move a device to such a position. In that patent, a sensor is used to identify the position of the winding tube driven by the actuator. In all cases it is up to the installer or user to store the intermediate position in memory for the first time. This is done with the aid of a switching device comprising control keys.
Patent EP 0 574 637 discloses ways of recording and executing a command to enable an intermediate position to be reached in the case of an actuator without a position sensor. Here it is the duration of the operation which is analyzed. An intermediate position is therefore expressed as a percentage of the total travel between the two extreme positions.
The disclosed devices have a drawback in that the intermediate or comfortable position must necessarily be set either by the installer or by the user. Furthermore, if this setting is not carried out, the user may remain unaware of the existence of this shading and ventilation position function.
In Application FR 02 03668, it was suggested that devices be produced comprising an intermediate position predefined by the manufacturer. In the case of a maker of roller blinds who knows the type of slat of each device, it is possible to determine this intermediate position information, for example as a percentage of the total travel. The main advantage of this prestored and predefined value is that it enables the installer to present the function to the customer and leave its precise adjustment to the customer, at the customer's convenience. It is not therefore necessary for the intermediate position to correspond to the best shading and ventilation position.
This device has a drawback—it complicates production, since the type of slat used in the roller blind must first be determined, and then this intermediate-position data must be stored in memory.